1. Field of the Invention
The present invention relates to a power generation control device and a power generation control method and, more particularly, to a power generation control device for controlling a power generation system of a movable body such as a vehicle and a power generation control method.
2. Description of the Relevant Art
Techniques for controlling outputs of a generator whose drive source is an engine of a vehicle (such as a generator driven through a belt by an engine of a vehicle) according to the running state of the vehicle have been proposed. For example, in the below-mentioned Patent Documents 1-3, techniques (charge control techniques) have been disclosed, wherein power generation by a generator is restricted when a vehicle is in an accelerating state so as to reduce a load on an engine. The purpose of restrictions on power generation by a generator in an accelerating state of a vehicle so as to reduce a load on an engine is to improve fuel consumption and accelerating performance of the vehicle.
In recent years, in order to increase the comfort of users, a large number of electronic devices (such as a seat heater and a mirror heater) which have no direct relation with running of a vehicle have been mounted on the vehicle, and therefore, a load on a battery has been increased.
However, with the increased number of electronic devices for comfort, it might become impossible to realize a stable power supply to traveling safety systems such as a pre-crash safety system, a brake assist system and an air bag system.
In order to solve this problem, there is a technique (load limiting technique) wherein a power supply to comfort systems is limited based on a quantity of electricity obtained by adding a quantity of electricity generated by a generator to a current (battery suppliable current) which can be taken out of a battery so as to secure a stable power supply to traveling safety systems with high importance.
By the way, in cases where the above-described charge control technique is adopted in a vehicle in which this load limiting technique has been adopted, load limitations are imposed more than necessary, and therefore, there is a possibility that the comfort may be damaged. An example is described with FIGS. 16(a)-16(c).
A battery suppliable current IBAT represents a quantity of electricity which can be taken out of a battery. A quantity of electricity generated IALT represents a quantity of electricity generated by a generator. A quantity of electricity obtained by adding the battery suppliable current IBAT and the quantity of electricity generated IALT is a quantity of electricity which a vehicle can discharge. An essential supply current ILD1 represents a quantity of electricity which is supplied to traveling safety systems, while a load working current ILD2 represents a quantity of electricity which is supplied to comfort systems.
FIG. 16(a) shows a situation where a quantity of electricity obtained by adding the battery suppliable current IBAT and the quantity of electricity generated IALT is larger than a quantity of electricity obtained by adding the essential supply current ILD1 and the load working current ILD2 in a constant speed state of the vehicle.
When the vehicle is accelerated, power generation by the generator is restricted by a ‘charge control technique’, and as shown in FIG. 16(b), the quantity of electricity generated IALT is reduced. As a result, the quantity of electricity obtained by adding the battery suppliable current IBAT and the quantity of electricity generated IALT becomes smaller than the quantity of electricity obtained by adding the essential supply current ILD1 and the load working current ILD2. When the quantity of electricity obtained by adding the battery suppliable current IBAT and the quantity of electricity generated IALT became smaller than the quantity of electricity obtained by adding the essential supply current ILD1 and the load working current ILD2, the load working current ILD2 is limited by a ‘load limiting technique’ as shown in FIG. 16(c).
That is, when the vehicle is in the accelerating state, power generation by the generator is restricted by the ‘charge control technique’ without relation with the situation of electric loads. And when the quantity of electricity generated IALT by the generator became smaller, a power supply to the comfort systems is limited by the ‘load limiting technique’ in order to secure a stable power supply to the traveling safety systems, and therefore, there is a possibility that load limitations may be imposed more than necessary.
The Patent Document 2 has disclosed that, in a technique for cutting off power generation by a generator when a vehicle is in an accelerating state, a cutoff of power generation is prohibited when a battery voltage value is a prescribed value or less (i.e. when the battery voltage value is high, power generation is cut off). However, when the rate of operation of electronic equipment is high, resulting in a heavy electric load, there is a possibility that load limitations may be imposed more than necessary even if power generation is cut off only when the battery voltage value is high.
The Patent Document 3 has disclosed that an output of a generator is restricted when a battery charging rate is a prescribed value or more. In this case, similarly to the above-described case, when the rate of operation of electronic equipment is high, resulting in a heavy electric load, there is a possibility that load limitations may be imposed more than necessary.    [Patent Document 1] Japanese Patent Application Laid-Open Publication No. 4-312326    [Patent Document 2] Japanese Patent Application Laid-Open Publication No. 2001-173481    [Patent Document 3] Japanese Patent Application Laid-Open Publication No. 7-274597